The windows of buildings have the drawback of contributing to the heating of the buildings in summer and to their cooling in winter.
Since the mid-1990s, a large variety of insulating and solar control windows have been developed by the glass industry. Thanks to “low emissivity” or “reflecting” coatings currently on the market, high levels of thermal insulation and of solar protection can be obtained.
Nevertheless, these windows have fixed properties which cannot be adapted to the temperature and sunshine conditions.
Window glass with variable optical properties provides a solution to this problem.
These active glass panes, referred to as “intelligent glass”, have optical transmission properties that are modifiable, for example electrically.
One known solution is to use electrochromic window glass to minimize the energy consumption of the building.
US-A-2007/0067048 describes a system for controlling electrochromic windows aiming to minimize the energy consumption of the building while at the same time providing a certain brightness inside of the building.
Nevertheless, electrochromic glass modifies the spectral distribution of the transmitted light, which can be a drawback, even if a user does not necessarily realize it.
Indeed, it will be a drawback for example in a museum if the colors of the works exhibited are modified, even in an unnoticeable manner for the visitor.
Furthermore, an environment even very slightly colored can produce certain psychological effects on the nervous system. Colors with a long wavelength (red) have a stimulating effect whereas colors with a short wavelength (violet) have a calming effect. The intermediate colors (yellow, green), have a tonic effect favorable to concentration.